Photosynthesis

How do plants get energy?
Photosynthesis – process plants use to trap sun’s energy and build carbohydrates (glucose) that store energy.
Formula:
6CO
2
+ 6H
2
O + energy → C
6
H
12
O
6
+ 6O
2
6 carbon dioxide + 6 water + energy→ 1 glucose + 6 oxygen

2 Phases of Photosynthesis

1.
2.

2 Phases of Photosynthesis:
1. Light-dependent Reactions
– Takes place in chloroplasts
– Chloroplast contains pigment called chlorophyll which is green because it reflects green light.
(In fall, trees absorb chlorophyll and other colors show through.) light energy (from Sun) → chemical energy (ATP)

2 Phases of Photosynthesis:
2. Light-independent Reactions or Calvin Cycle or Dark Reactions
– Does not require light
– Uses ATP (from light reactions) to convert CO
2 glucose to

How do plants regulate water & gas exchange?
Guard cells on the underside of leaves open to let in CO
2 and O
2
(waste product) and some
H
2
O out (plant “sweating”). The cells are closed when they become flaccid & lose water. The cells open when they are full of water & swollen. This process is called transpiration.

Guard Cells

Guard Cells